class Base{
    int a;
    int b;
    public void method(){
        System.out.println("method方法");
    }
}
class Derived extends Base{
    // super(); // 注意子类构造方法中默认会调用基类的无参构造方法：super(),
    // 用户没有写时,编译器会自动添加，而且super()必须是子类构造方法中第一条语句，
    // 并且只能出现一次
}

public class Test {
    public static void main(String[] args) {

    }
}

class Student {

}

class Teacher {

}

class School {
    public Student student;
    public Teacher teacher;
}
